Marking the liquids for their distinguishing is know from the prior art for a relatively long time. For the first time an organic dye was used to identify Pb-containing fuels already in 1926. Later on the dye additions were used to mark gasoline sold exclusively for the use in agriculture, or for marking vehicles that had paid highway taxes and for a number of other purposes. At present all bigger oil companies such as Shell, Unocal, Arco, Chevron, Lukoil etc. use different dye additives for marking different gasoline brands (Kaplan, I. et al “Organic Geochemistry” 27(5), 289-317, 1997). The main purpose for using marking additives is to identify the origin of gasoline, first of all in connection with taxation or environment protection.
The more general purpose of using markers is to create liquid identity in order to distinguish specific liquid from similar liquids. In case the marker is not detected in a presumably marked liquid, then this indicates that the liquid is not original. When the marker is detected in a liquid, then this indicates that the liquid comes from its' actual producer. The last statement is valid only on a precondition that the marker is not falsified and that it is the same one as was used in original products' marking process. In many cases for increasing marking security it is preferable to use such marking that the marker contained in the marked product is not visible to regular user, but is detectable by an authorized user (i.e. official customer). Such marking is referred to as “hidden marking”.
However, despite of a rapid elaboration and active use of “hidden marking” methods the “hidden marking” does not guarantee really effective identification of factual origin of liquids, including fuels, and does not prevent their illegal use, blending or counterfeit, neither does it make possible to identify a real polluter of the environment after the liquid has been spilled to the ground or flown to water reservoirs. This is due to following several reasons.    i) It is possible to simulate or camouflage analyses results by adding similar additives.    ii) For identifying marked liquid sampling together with following detailed laboratory analyses is necessary, due to which the identification process is often time consuming and costly. The marking methods used at present are without exceptions based on laboratory analyses.    iii) The know so far ways of “hidden marking” are in a considerable scale influenced by human factor. Even in case the used recipe of markers or marking procedure are secret, or a specific detection procedure is used, there exists a potential danger of their disclosing or discovering.
In order to overcome the recited shortcomings different improvements of marking and analysing methods have been proposed.
In order to overcome shortcomings indicated above in (i) new markers have been developed which are hard to eliminate from the fuel by simple chemical or physical procedures, as for example C16-C26-n-alkane) (RU 2 199 574, Rubanik, S. I. et al “Chemical marker”, but especially markers which can be added in small quantities, as for example 1,4-dimethyl-2-nitro-benzene (EP 0 385 441, Papa Sisto Sergio “Marker for petroliferous products”), C1-C6 alkyl (U.S. Pat. No. 5,205,840, Friswell Michael R. “Markers for petroleum, method of tagging and method of detection”) and composite markers (U.S. Pat. No. 4,209,302, Orelup, Richard B. “Marker for petroleum fuels”), and which can be detected by easy laboratory tests. They include colorless markers which become visible after adding chemical reagent (WO 9 632 462, Desaj Bkharat, et al “Composition including thymol-phthaleine marker, method and solution for marking petroleum product, and a method for identification of petroleum product”), or specific combinations of markers mutually cancelling each other's colour when introduced into liquid (U.S. Pat. No. 6,294,110, Zimin Sr Al, et al “Colour cancelling marking systems”. Some developments are connected with markers requiring a unique detection procedure in order to obtain more secure marking.
In order to overcome shortcomings indicated in (ii) methods and marking systems have been worked out for automation of marking and identification processes, resulting in simplification of marking and identification of liquids. In document WO 0 240 274 (Altenkirche, Günter et al “Marking device and extrusion system with a marking device of this type” a precise pumping system for marking of liquids is described. In a document WO 02 098 199 (Sochin, Moshe et al “Method and system for marking and determining the authenticity of liquid hydrocarbons” a microprocessor controlled marking and identification of a liquid flowing from a source (cistern) to a destination (storage tank).
In practice the combinations of markers or compound materials are used for marking. In document U.S. Pat. No.5,958,780 is described a marking system, which is based on the predefined concentration ratio of at least two markers miscible with the liquid. The ratio of a second marker concentration and first marker concentration, which is defined using optical absorption spectrum or fluorescence radiation spectrum, is compared with predefined value to identify the liquid.
In spite of numerous improvements made in marking and identification technologies the problem indicated above in (iii) is still not solved and hampers achieving of a totally secure marking. In addition, revealing of what so ever unique features concerning markers, marking and identifying processes is possible (either by steeling the information, selling the information to the interested third parties, etc), which makes falsification of a marked liquid possible.
In present invention a fully automatic marking method and a marking system for applying this method are proposed, by means of which all disadvantages indicated above in (i) to (iii) have been eliminated. This was possible due to the following.
In this invention no such secret information is used which in reality could be disclosed to the interested entities. According to the invention a variety of different and suitable for that purpose markers can be used, whereby data concerning markers used for marking is contained in encrypted code, and it is possible to alter the markers and their concentration for any batch of liquid to be marked next (please see point (i) above). The identification procedure proposed in the invention can be carried out on-site (in real time) in a simple and fast manner without a need for laboratory analyses (please see point (ii) above).
Marking and identifying process are automatic using encrypting/decrypting means, in which case the influence of human factor as such is practically excluded (please see (iii) above).